demjson (version 1.2, 2007-11-08) | index demjson.py |
A JSON data encoder and decoder.
This Python module implements the JSON (http://json.org/) data
encoding format; a subset of ECMAScript (aka JavaScript) for encoding
primitive data types (numbers, strings, booleans, lists, and
associative arrays) in a language-neutral simple text-based syntax.
It can encode or decode between JSON formatted strings and native
Python data types. Normally you would use the encode() and decode()
functions defined by this module, but if you want more control over
the processing you can use the JSON class.
This implementation tries to be as completely cormforming to all
intricacies of the standards as possible. It can operate in strict
mode (which only allows JSON-compliant syntax) or a non-strict mode
(which allows much more of the whole ECMAScript permitted syntax).
This includes complete support for Unicode strings (including
surrogate-pairs for non-BMP characters), and all number formats
including negative zero and IEEE 754 non-numbers such a NaN or
Infinity.
The JSON/ECMAScript to Python type mappings are:
---JSON--- ---Python---
null None
undefined undefined (note 1)
Boolean (true,false) bool (True or False)
Integer int or long (note 2)
Float float
String str or unicode ( "..." or u"..." )
Array [a, ...] list ( [...] )
Object {a:b, ...} dict ( {...} )
-- Note 1. an 'undefined' object is declared in this module which
represents the native Python value for this type when in
non-strict mode.
-- Note 2. some ECMAScript integers may be up-converted to Python
floats, such as 1e+40. Also integer -0 is converted to
float -0, so as to preserve the sign (which ECMAScript requires).
In addition, when operating in non-strict mode, several IEEE 754
non-numbers are also handled, and are mapped to specific Python
objects declared in this module:
NaN (not a number) nan (float('nan'))
Infinity, +Infinity inf (float('inf'))
-Infinity neginf (float('-inf'))
When encoding Python objects into JSON, you may use types other than
native lists or dictionaries, as long as they support the minimal
interfaces required of all sequences or mappings. This means you can
use generators and iterators, tuples, UserDict subclasses, etc.
To make it easier to produce JSON encoded representations of user
defined classes, if the object has a method named json_equivalent(),
then it will call that method and attempt to encode the object
returned from it instead. It will do this recursively as needed and
before any attempt to encode the object using it's default
strategies. Note that any json_equivalent() method should return
"equivalent" Python objects to be encoded, not an already-encoded
JSON-formatted string. There is no such aid provided to decode
JSON back into user-defined classes as that would dramatically
complicate the interface.
When decoding strings with this module it may operate in either
strict or non-strict mode. The strict mode only allows syntax which
is conforming to RFC 4627 (JSON), while the non-strict allows much
more of the permissible ECMAScript syntax.
The following are permitted when processing in NON-STRICT mode:
* Unicode format control characters are allowed anywhere in the input.
* All Unicode line terminator characters are recognized.
* All Unicode white space characters are recognized.
* The 'undefined' keyword is recognized.
* Hexadecimal number literals are recognized (e.g., 0xA6, 0177).
* String literals may use either single or double quote marks.
* Strings may contain \x (hexadecimal) escape sequences, as well as the
\v and \0 escape sequences.
* Lists may have omitted (elided) elements, e.g., [,,,,,], with
missing elements interpreted as 'undefined' values.
* Object properties (dictionary keys) can be of any of the
types: string literals, numbers, or identifiers (the later of
which are treated as if they are string literals)---as permitted
by ECMAScript. JSON only permits strings literals as keys.
Concerning non-strict and non-ECMAScript allowances:
* Octal numbers: If you allow the 'octal_numbers' behavior (which
is never enabled by default), then you can use octal integers
and octal character escape sequences (per the ECMAScript
standard Annex B.1.2). This behavior is allowed, if enabled,
because it was valid JavaScript at one time.
* Multi-line string literals: Strings which are more than one
line long (contain embedded raw newline characters) are never
permitted. This is neither valid JSON nor ECMAScript. Some other
JSON implementations may allow this, but this module considers
that behavior to be a mistake.
References:
* JSON (JavaScript Object Notation)
<http://json.org/>
* RFC 4627. The application/json Media Type for JavaScript Object Notation (JSON)
<http://www.ietf.org/rfc/rfc4627.txt>
* ECMA-262 3rd edition (1999)
<http://www.ecma-international.org/publications/files/ecma-st/ECMA-262.pdf>
* IEEE 754-1985: Standard for Binary Floating-Point Arithmetic.
<http://www.cs.berkeley.edu/~ejr/Projects/ieee754/>
Classes | ||||||||||||||||||||||||||||||||||
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Data | ||
__author__ = 'Deron Meranda <http://deron.meranda.us/>' __credits__ = 'Copyright (c) 2006-2007 Deron E. Meranda <http:/...m. If not, see <http://www.gnu.org/licenses/>.\n\n' __date__ = '2007-11-08' __version__ = '1.2' content_type = 'application/json' file_ext = 'json' hexdigits = '0123456789ABCDEFabcdef' i = 31 inf = inf nan = nan neginf = -inf octaldigits = '01234567' undefined = demjson.undefined unsafe_string_chars = '"\\\x00\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1a\x1b\x1c\x1d\x1e\x1f' |
Author | ||
Deron Meranda <http://deron.meranda.us/> |
Credits | ||
Copyright (c) 2006-2007 Deron E. Meranda <http://deron.meranda.us/> Licensed under GNU GPL 3.0 or later. See LICENSE.txt included with this software. This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program. If not, see <http://www.gnu.org/licenses/>. |